Scott Todd wrote:Castellated don't get torqued. They are for shear loads where parts need to rotate.
Not always true and I don't think that is true in this case. Not every location that a castellated nut is used is subject to rotation. There are places where heat or vibration or a number of other issues can warrant the use of a castellated nut. For those types of conditions where the nut/bolt is not subject to rotation (likely in the motor-mount example being asked above) the nut should be torqued to the same torque as a locking nut (50-70 inch/pounds for AN4). For areas that a nut is used that are subject to rotation (think aileron bell cranks on the Sonex) that nut should be tightened snug but not to exceed the standard torque requirement (50 to 70 inch/pounds for AN4).
If you don't have a copy I suggest buying or downloading a copy of AC 43.13. There is a wealth of information in there that will help you answer questions like this when building.
Keith
#554